This might be an unpopular opinion, but I think Deceit is actually the one most at fault for Thomas deciding to go to the wedding instead of the callback - not for any like unsympathetic reasons or anything like that, but because the way he handled the situation just made it So Much Worse (but was also very in character), even if he was fighting for what was probably the best thing to do
The reason most episodes end with a satisfying conclusion is that the light sides (including Virgil) usually have an argument as equals and then end with a compromise, but Deceit just Doesn't Do That
And, honestly, that's pretty in character for him. His job is to prioritise Thomas/himself over everything/everyone else (selfishness, basically), so of course he doesn't want to compromise/consider the possibility that he might be wrong, or let others decide what to do. This is honestly why I think he's gonna be the last to be accepted - I mean, Virgil also had to realise he was going too far to be accepted (though he ended up going too far in the wrong direction), but that was in character for him, as his job is protecting Thomas through putting him/himself down (which is like the opposite to Deceit, which is interesting cos they're both self preservation)
ANYWAY I'm getting off track
I fully believe that if Deceit hadn't turned SVS into the Courtroom Scenario where he was going one-on-one against Patton, and had had an Actual Debate with the other sides, he would have easily gotten Roman AND Logan on his side, and would've been able to go to the callback - for two main reasons.
One - the whole "making thomas feel like he's been accused of a crime" strategy was Very Stupid and led to him (and Roman) feeling guilty (duh) and deciding to go to the wedding anyway. VERY stupid move for Deceit, what made him think that would work????? Telling someone that they're guilty and then expecting them not to feel bad and want to "do better" is DUMB
And two! He made it a Deceit vs Patton when it could've been Deceit and Roman (and maybe Logan) vs Patton (and Virgil, though I bet he's only really on that side cos he doesn't wanna support Deceit). He could have so easily won like that!!!!! An argument as equals (maybe if he needed a scenario he could've made it a Proper Debate) can lead to a compromise
He put so much work into controlling the whole situation, and refusing to compromise or have a fair debate, that of course things didn't go his way. Thomas should've chosen to go to the callback, but Deceit ended up pushing him to go to the wedding
Honestly? If he wasn't involved in that episode at all they probably could've come to the conclusion that going to the callback (and being Honest about it) was the better plan.
Patton can be persuaded to go against what he wants to do, it's literally happened in the past - though it might've been a challenge, I think Roman (and Logan) would've been able to succeed - especially cos just talking to his friends about this could've solved the situation easily! But Deceit put him in a position where he was forced to Defend Thomas and think that going to the callback was just Thomas giving it to his secret dark desires (which Patton, as morality, naturally wouldn't like)
So, yeah, I think it's Deceit's fault that they're going to the wedding. But if you disagree, it's fine! We can agree to disagree lol - or you can start a Friendly Debate if you like, as long as it doesn't turn into an argument/dip into unsympathetic light sides territory (as that makes me uncomfortable)